The length of a rectangle is 3 inches more than twice its width, and its area is 65 square inches. What is the width?If w = the width of the rectangle, which of the following expressions represents the length of the rectangle?

2w + 3
2(w + 3)
3(2w)

Answers

Answer 1
Answer: Let L be the length of the rectangle and W be its width. Translating the first sentence into mathematical expressions, we get, L=2W+3. To get the area of a rectangle, we will use the formula A=L*W. Since we are already given with the area, we will substitute this value to the formula, together with the expression of L in terms of W. Thus, 65=(2W+3)*(W). Further simplification would yield

65=2W^2+3W
2W^2+3W-65=0

We have a quadratic equation, hence, we will solve for its factors. We have,

(2w+13)(w-5)=0

The two roots of the equation are: -13/2 and 5. Since we can only have positive numbers for dimensions, the width of the rectangle is 5 in. 

The expression for the length of the rectangle is 2W+3.

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The sides of a triangle are in the ratio 3 : 4 : 5. What is the length of each side if the perimeter of the triangle is 90 cm?

Answers

what we can do is set up an algebraic equation. 

our variable can me L for Length

3L+4L+5L=90

now all we have to do is solve

12L=90
----   ----
12      12

L=7.5

now multiple each number in the ratio by 7.5 to find out how long each side is

3 times 7.5 is 22.5
4 times 7.5 is 30
5 times 7.5 is 37.5

the side lengths are 22.5, 30, and 37.5

Suppose you choose a marble from a bag containing 4 red marbles, 2 white marbles, and 3 blue marbles. You return the first marble to the bag and thenchoose again. Find P(red and blue).
A. 4/3
B. 2/3
C. 7/9
D. 4/27

Answers

Your probality would be C. 7/9

If angle 1 and angle 7 are vertical angles and angle 1 and angle 2 are supplementary adjacent and the measure of angle 2 is 123 degrees. what is the measure of angle 7?

Answers

Answer:  m∡7 = 57° .
_________________________________

Explanation:
____________________
 m∡7 = m∡1 ;  SInce  these angles are vertical; and vertical angles are congruent.

m∡1 + m∡2 = 180 ; since these angles are supplementary; and by                                            definition; supplementary angles "add up" to 180.

Given: m∡2 = 123 ;  

m∡1 + 123 = 180 ;

Since m∡1 = m∡7 ; and we wish to find: "m∡7" ;  we can rewrite as:
_______________________________
m∡7 + 123 = 180 ; solve for "m∡7" ;
_______________________________
Subtract "123" from EACH SIDE of the equation:
_________________________________________
  m∡7 + 123 - 123 = 180 - 123 ;
_________________________________________
  m∡7 = 57° .
_________________________________________

What is the value of x in this figure?123√

122√

63√

6

A right triangle with both legs shown with one tick mark. One of the legs is labeled 12. The hypotenuse is labeled x.

Answers

Here we use the Pythagoras theorem

According to this, in a right angled triangle, the sum of the squares of the lengths of the two sides is equal to the hypotenuse

is "a" and "b" are the sides, and "h" is the hypotenuse, then :

a^(2)+  b^(2) = h^(2)

In the given problem, a = b = 12 and h = x

12^2 + 12^2 = x^2

So, x =\sqrt{12^(2)  + 12^2

x = √(144 + 144)

X =√(288)

X = 12√(2) (Option B)

The answer is the second choice, 12√2

SOLVING SYSTEMS OF EQUATIONS BY SUBSTITUTION.

1. 2x+3y=1
-3x+y=15

Answers

2x+3y=1 \n-3x+y=15 \n \n\hbox{from the 2nd equation:} \n-3x+y=15 \ny=15+3x \n \n\hbox{substitute 15+3x for y in the 1st equation:} \n2x+3(15+3x)=1 \n2x+45+9x=1 \n9x+2x=1-45 \n11x=-44 \nx=-4 \n \n\hbox{solve one of the equations for y}: \n2x+3y=1 \n2 \cdot (-4) + 3y=1 \n-8+3y=1 \n3y=1+8 \n3y=9 \ny=3 \n \n\hbox{the answer:} \nx=-4 \ny=3

Determine the dimensions of the rectangle of largest area that can be inscribed in a semicircle of radius 4

Answers

Answer:

The length and width that maximize the area are:

W = 2*√8

L = 2*√8

Step-by-step explanation:

We want to find the largest area of a rectangle inscribed in a semicircle of radius 4.

Remember that the area of a rectangle of length L  and width W, is:

A = L*W

You can see the image below to see how i will define the length and the width:

L = 2*x'

W = 2*y'

Where we have the relation:

4 = √(x'^2 + y'^2)

16 = x'^2 + y'^2

Now we can isolate one of the variables, for example, x'

16 - y'^2 = x^'2

√(16 - y'^2) = x'

Then we can write:

W = 2*y'

L = 2*√(16 - y'^2)

Then the area equation is:

A = 2*y'*2*√(16 - y'^2)

A = 4*y'*√(16 - y'^2)

If A > 1, like in our case, maximizing A is the same as maximizing A^2

Then if que square both sides:

A^2 = (4*y'*√(16 - y'^2))^2

      = 16*(y'^2)*(16 - y'^2)

      = 16*(y'^2)*16 - 16*y'^4

      = 256*(y'^2) - 16*y'^4

Now we can define:

u = y'^2

then the equation that we want to maximize is:

f(u) = 256*u - 16*u^2

to find the maximum, we need to evaluate in the zero of the derivative:

f'(u) = 256 - 2*16*u = 0

      u = -256/(-2*16) = 8

Then we have:

u = y'^2 = 8

solving for y'

y' = √8

And we know that:

x' = √(16 - y'^2) = √(16 - (√8)^2) = √8

And the dimensions was:

W = 2*y' = 2*√8

L = 2*y' = 2*√8

These are the dimensions that maximize the area.